The present invention relates to an ultrasonic diagnosis apparatus, and more particularly to an ultrasonic diagnosis apparatus provided with a digital signal processor suitable for clearly defining the contour of an ultrasonic image by emphasizing the high frequency components of an envelope signal.
In a conventional circuit for emphasizing the contour as disclosed in JP-A-55-120859, a part of an envelope signal is high-frequency cut and inverted through an inverter amplifier. The obtained signal is added to the original envelope signal to emphasize the high frequency components thereof. Thus, a conventional circuit processes an envelope signal in an analog manner. The circuit arrangement of the analog signal processing method disclosed in JP-A-55-120859 is shown in FIG. 1.
In the Figure, the circuit is constructed of a probe 201, a transmission control circuit 202, a reception control circuit 203, a phase adjustment circuit 204, an amplifier 205, a detector circuit 206, a circuit for emphasizing the high frequency components of an envelope signal (hereinafter called an FTC circuit), an A/D converter 208, a frame memory 209 and an ultrasonic image display unit 210.
In the above circuit arrangement, an ultrasonic signal transmitted from and received to the probe 201 is supplied to the circuit elements 203 to 206 to detect its envelope signal whose high frequency components are emphasized by the FTC (Fast Time Constant) circuit 207. The emphasized signal is converted into a digital signal by the A/D converter 208 to be stored in the frame memory 209. An ultrasonic image is displayed on the ultrasonic display unit 210 in accordance with the information stored in the frame memory 209. As above, the envelope signal processing before the A/D converter 208, particularly at the FTC circuit, is analog. Since the circuit performance varies depending on the dispersion of circuit component tolerances, a fine adjustment requiring considerable work and time is necessary, resulting in high cost.Further, in view of the above circumstances, it is difficult to readily change the circuit performance.
Furthermore, no measure has been proposed against the problem that the circuit performance varies due to the dispersion of circuit component tolerances. For example, there arises a problem that if a plurality of signal processor circuits are used for processing a plurality of received ultrasonic signals, each displayed image may have a nonuniformity in brightness due to a difference in each circuit performance.